A Study On The Distribution And Potential Impact Of Climate Change On The Invasion Of Sunflower Potato In China Based On A Random Forest Model

Biological invasion has become a hot issue of global ecological security,which has changed the ecological balance and biodiversity of the original ecosystem in many parts of the world.In the context of climate change,biological invasion can't be ignored.Therefore,in order to reduce the ecological,economic and security losses caused by invasive species,we need to identify areas with high invasion risk and areas that have caused invasion risk.Species distribution model(SDM)is an effective tool to predict species distribution,and it is also the most widely used method to predict species distribution.As the second group of invasive species in China,Anredera cordifolia(Tenore)Steenis has caused huge ecological security problems in Southeast China.It is of great practical significance for the protection of ecological environment and ecological diversity in China to study its potential distribution and analyze the leading factors affecting its growth.In this study,in the current period,194 sampling sites data and climate,topography,soil and human activity factors related to the growth of A.cordifolia are used.After screening,13 climate factors,3 terrain factors,8 soil factors and human activity factors are obtained,and they are divided into 3 data sets.Based on the random forest model(RF)and geographic information system(GIS),the potential distribution of A.cordifolia in the current period and the impact of soil and human activities on the potential distribution of A.cordifolia in the current period were predicted;in the future(2050s and 2070s)19 climate factors,3 terrain factors and 8 soil factors were selected and divided into 2 data sets to analyze the impact of soil factors on the distribution of A.cordifolia under climate change;the dominant environmental factors and the thresholds of the dominant environmental factors were screened through the factor contribution rate and factor response curve of each environmental factor in the current period;to explore the trend of area expansion and contraction and the transfer of habitat centroid from the present to the future;to analyze the impact of climate change on the distribution and habitat change in different periods,to find areas with potential invasion risks,and to provide theoretical support for the removal,management and prevention of A.cordifolia.The main conclusions are as follows:(1)At present,the suitable habitats of A.cordifolia are mainly distributed in the south of China,and its climate is mainly tropical subtropical monsoon climate.At present,the total suitable habitat area accounts for 7.49%of the total area of China.Among them,the high suitable habitat accounts for 4.19%of the total suitable habitat,the medium suitable habitat and the low suitable habitat account for 35.87%and 59.94%of the total suitable habitat,respectively.Overall suitable habitat terrain includes Sichuan Basin,Yunnan Guizhou Plateau and Southeast hills.(2)The prediction and evaluation values of the three evaluation indexes for each period are all of high precision,and the evaluation results are AUC(0.961-0.98)>TSS(0.826-0.883)>Kappa(0.783-0.854),of which AUC is the highest,with an average value of 0.97,followed by TSS and Kappa,with an average value of 0.86 and 0.81,respectively.(3)Compared with the current environment factor data sets ?1 and ?1,and the future environment factor data sets ?2 and ?2,it is found that the suitable habitat of A.cordifolia predicted by adding soil factors(data sets ?1)is more consistent with the actual distribution,and the prediction result of adding soil factors(?2)in the future is more accurate.The soils in southern cities such as Guangxi and Guangdong are mostly latosol and red soil,which are similar to the original soil conditions of A.cordifolia,so the results obtained by adding soil factors are more accurate.(4)Compared with data sets ?1 and ?1,it was found that the suitable habitat level predicted by increasing human activity factor(data set ?1)was more consistent with the density of collected point data.In the northwest of China,the intensity of human activities is the weakest,and the potential suitable habitat of the A.cordifolia is unsuitable,probably there is no corresponding human introduction;the intensity of human activities in the eastern coastal area is higher,and the A.cordifolia is also medinm and high suitable habitat in the eastern coastal area,which shows that there are more human introduction in these areas.Over time,other regions may also increase the introduction of A.cordifolia,new suitable habitats may appear or the range of current suitable habitats may be expanded.(5)There are 10 main environmental factors that affect the distribution of sunflower tuber,which are Bioll(Mean temperature of coldest quarter),Bio7(Temperature annual range),HFP(Human footprint data set),Bio9(Mean temperature of driest quarter),Bio18(Precipitation of the warmest quarter),Bio4(Temperature seasonality),Bio12(Annual precipitation),Bio 2(Mean diurnal temperaturerange),Bio 1(Annual mean air temperature),Bio16(Precipitation of the wettest quarter).By analyzing the average value,standard deviation and the optimal physiological threshold value of the main environment factors,the results show that the suitable habitat for A.cordifolia is the tropical subtropical monsoon area with mild winter and little rain,abundant rainfall and sufficient heat in summer.(6)In the future climate change,the expanding habitat of A.cordifolia has been in the Yunnan Guizhou Plateau and the Guangdong and Guangxi hilly areas.In 2050s,the change range of habitat grade is relatively large,it is stay in stable-expansioncontraction,and its habitat state is very unstable,and gradually adapted to the local environment to form a stable habitat in 2070s,Therefore,the habitat center of gravity moved southward.